Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability and autism spectrum disorder, with an estimated frequency of about 1:4000-5000 in males and about 1:8000 in females. It affects all racial and ethnic groups worldwide. Despite the years of work, there are still considerable gaps in our knowledge about the natural history of FXS and the needs of individuals and families with FXS. Studies of co-occurring conditions have typically focused on each condition alone by using cross-sectional data, without examining the associations with other features of FXS or without taking a systems approach. Furthermore, in order to conduct well-designed clinical trials that capture the entire spectrum of the disorder, the natural history of those with FXS needs to be determined. This is particularly true for adults with FXS, about whom almost nothing is known regarding life trajectory and medical complications. The Fragile X Online Registry With Accessible Research Database (FORWARD) was implemented in 2012 to fill the recognized gap in knowledge. FORWARD consists of a patient and family registry and a longitudinal database populated by clinician- and parent-reported data from individuals living with FXS. Fragile X clinics that are members of the Fragile X Clinical and Research Consortium, in partnership with the National Fragile X Foundation and the Centers for Disease Control and Prevention, have contributed clinician- and parent- reported data to FORWARD. Currently, the database includes over 850 participants with FXS with a baseline data collection point. The longitudinal component now includes over 250 subjects with follow-up data. The goals of this proposal are to expand FORWARD by: 1) increasing the number of baseline and longitudinal data points, 2) building new data collection tools to enroll and characterize adults with FXS, and 3) expanding efforts to increase the number of participants who are currently under-represented in FXS studies Through analyses coordinated with Component B, the resulting longitudinal cohort characterized in FORWARD will allow the fragile X clinical research and public health community to examine changes over time in use of treatments and services, educational setting, medical problems, and other characteristics obtained from a combination of parent and clinician report. To our knowledge, FORWARD is now the largest collection of data about individuals with FXS attending specialty clinics, with the added value of the collection of clinician- reported information. The expansion proposed in this application, in combination with the detailed longitudinal cognitive, adaptive, language, motor, behavioral, social, and quality of life data to be collected at the combined Component C sites, is essential to further our understanding of the natural history of FXS and the needs of individuals and families with FXS across their life spans.